The paper presents a new approach for planning high voltage transmission networks. The developed simulation model takes into account the capital investment cost in its discrete form as well as the cost of transmission losses. The constraint equations include the DC load flow equations and line loading constraints. The voltage loop equations are written in a modified form, such that a closed-loop equation will be ineffective if any line of this loop is deleted. The simulation model utilises the mixed-integer linear programming technique to obtain the least-cost network satisfying line loading constraints. Verification of the method is made through a test example. List of symbols NS(i) = number of states of proposed line i Cij Z i j Bij P i j b, PR, M 1 M 2 S , = capital cost of statej of proposed line i = zero-one integer variable assigned to state j of = cost of transmission losses for unit power trans-= power flow on state j of proposed line i = cost of transmission losses of unit power transmitted on existing line i = power flow on existing line i = number of proposed lines = number of existing lines = linearised cost coefficient representing transmis-= linearised cost coefficient representing transmis-F = value of actual system cost (capital plus transXi = reactance of proposed line i assuming definite Pi = power flow on proposed line i X , , = reactance of existing line i K M = a large positive integer number P M ; = maximum power flow of proposed line i K l(i) = set of proposed lines connected to busbar i K2(i) = set of existing lines connected to busbar i Ll(i) = set of existing lines forming basic loop i which proposed line i mitted on statej of proposed line i sion losses cost of state j of proposed line i sion losses cost of existing line i mission losses cost) number of circuits contains existing lines only Paper 6095C (B), first L2(i) = set of existing lines forming basic loop i which Hi = injected power at busbar i LB1 = number of basic loops containing existing lines LB2 = number of basic loops containing existing lines Q M , = maximum power flow of existing line i X P i j = reactance of statej of proposed line i P M i j = maximum power flow of state j of proposed line i N B , = minimum number of proposed lines connected to N = number of busbars F' contains one proposed line only plus one proposed line busbar i = value of linearised system cost 1
Summary
This paper presents a mixed integer nonlinear programming (MINLP) model to solve the conductor gradation optimization problem of radial distribution systems. The conductor size selection and capacitor allocation problem are solved using exact AC load flow equations. The dynamic load characteristics have been considered in this model. The main objective is to realize both the thermal limit constraints and the bus voltage limit constraints. This is done while minimizing the capital cost of the conductors, the capacitors costs, and the energy loss cost of the different conductors. A 117‐bus radial feeder system has been considered to verify the presented nonlinear model.
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